PD is the second most common neurodegenerative disease worldwide and affects more than one percent of people older than sixty years of age and roughly four percent of those older than 85 (de Lau et al. The Lancet Neurology 5, 525-535 (2006)). Currently, there is no simple and reliable diagnostic test for PD. It remains essentially a clinical diagnosis, subject to variations in patient presentation and physician awareness. Upon post-mortem examination, it has been estimated that only 80% of patients clinically diagnosed with PD have typical post-mortem neuropathological changes (Hughes et al. Archives of neurology 50, 140-148 (1993)). Even in subjects with an apparently positive response to dopaminergic medication, a clinical diagnosis of PD can have relatively poor accuracy (Adler et al. Neurology 83, 406-412 (2014)). Results are far worse for very Early-Stage PD subjects (Adler et al. Neurology 82, 858-864 (2014)). Neuroimaging approaches such as DaT scanning have some utility, but are expensive, invasive, and not very specific. Detection of biomarkers in the cerebrospinal fluid (CSF) or blood, presumably associated with PD pathogenesis, such as alpha-synuclein or DJ-1, has so far failed to yield consistent results (Hong et al. Brain: a journal of neurology 133, 713-726 (2010), Gerlach et al. Journal of neural transmission 119, 39-52 (2012), van Dijk et al. European journal of neurology: the official journal of the European Federation of Neurological Societies 21, 388-394 (2014), Mollenhauer et al. Experimental neurology 213, 315-325 (2008), and Aerts et al. Neurobiology of aging 33, 430 e431-433 (2012). Thus, there remains a great need for an accurate, inexpensive, and noninvasive test that can detect PD in its earliest stages.